This invention relates to a tape recorder, and more particularly to a tape recorder whose reel mechanism is fitted with a pair of one-way clutches. With the conventional tape recorder, a tape rewind is carried out by actuating an idler changeover mechanism, reversing the drive of a motor, and letting a supply reel act as a takeup reel. However, the prior art tape recorder in which the idler operation is changed over for a tape rewind has the drawback that an idler changeover mechanism has to be provided, undesirably enlarging and complicating the arrangement. The Japanese Patent Disclosure No. 10606/75 disclosed a tape recorder whose reel mechanism was fitted with a pair of one-way clutches to eliminate the above-mentioned idler changeover mechanism. This proposed tape recorder was of the dual capstan system and comprised a first endless belt stretched over a motor pulley and a pair of flywheels, and a second endless belt stretched over the motor pulley and a pair of reels each fitted with a oneway clutch. The belts were made to run in a prescribed direction by the normal or backward drive of a motor. The reproduction or recording mode or fast forward or rewind mode of a tape run was effected by the abovementioned process. In this case, however, the endless belt was required to have a certain thickness, presenting difficulties in reducing the thickness of the reel mechanism. The prior art had further drawbacks that the endless belt indicated unsatisfactory temperature characteristic and was ready to be broken, extended or contacted, making it difficult to ensure a stable tape run. Provision of two endless belts and two capstan shafts unavoidably increased the number of parts and enlarged and complicated the arrangement of a tape recorder as a whole.